Do sprint intervals to lose fat and improve conditioning—save time too. Research shows that high-intensity sprints are the only form of conditioning to produce significant fat loss.
A recent study, published in the Journal of Sports Science and Medicine, compared the effect of a 4-month sprint interval running program with an endurance running program on body composition, aerobic capacity, and time in a half-marathon race.
The sprint interval protocol varied each day, but an example of one of the workouts used was 10 intervals of 30-sec all-out sprints with 90 seconds active rest. The endurance protocol consisted of running at 75 to 85 percent of the lactate threshold for 45 to 75 minutes. Training time was matched with both training programs taking 2.5 hours total a week.
Results showed that the sprint interval group lost more body fat and more visceral belly fat than the endurance running group: The sprint group lost 1 kg of visceral fat and 2 kg of total body fat, while only losing 1 kg of lean mass.
To put it in perspective, the sprint interval group lost 16 percent belly fat compared to the endurance running group that had no significant loss of visceral belly fat, but did lose 1 kg of total body fat and 1.4 kg of lean mass, producing a less favorable body composition.
In addition, the sprint training group had greater improvements in resting heart rate and peak oxygen uptake than the endurance training group, indicating greater cardiovascular benefits. Sprint training also improved running speed at the lactate threshold by 20.5 percent compared to only 12.9 percent in the endurance group.
This was likely due to the fact that high-intensity training improved the use of fat for fuel, which leads to less glycogen being used for energy. Plus, being able to run faster with less exertion led to a much faster finish in the half-marathon time trial—the sprint group finished nearly three minutes faster than the endurance training group!
In terms of results, here are some of the benefits you can get from sprint training:
It elevates fat-burning hormones such as growth hormone.
It increases excess post-exercise oxygen consumption (the amount of energy burned in the 24 hours after exercise as the body recovers) much more than steady-state training.
It takes less training time. Typically, you can get similar or greater improvements in performance in half the training time when doing sprints compared to steady-state conditioning.
The only possible drawback to sprint training is that it is mentally challenging to push through an all-out workout even if it is short. The upside is that many trainees find intervals to be less boring than endurance training, and they enjoy feeling powerful and fast from going all out. Finally, the fact that the hard work you are doing will produce fat loss results is often enough to keep you going through a difficult, but short, workout.